Resid hydrotreating catalyst containing titania

ABSTRACT

Improved catalyst supports, supported catalyst, and method of preparing and using the catalysts for the hydrodesulfurization of a residuum hydrocarbon feedstock are disclosed. The catalyst supports comprise titania alumina having 5 wt % or less titania and have greater than 70% of their pore volume in pores having a diameter between 70 Å and 130 Å and less than 2% in pores having a diameter above 1000 Å. Catalysts prepared from the supports contain Groups 6, 9 and 10 metals or metal compounds, and optionally phosphorus, supported on the titania alumina supports. Catalysts in accordance with the invention exhibit improved sulfur and MCR conversion in hydrotreating processes.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/409,560, filed on Dec. 19, 2014, which is a national phaseentry under 35 U.S.C. §371 of International Application No.PCT/US2013/046753 filed Jun. 20, 2013, which claims priority from U.S.Provisional Patent Application No. 61/662,003 filed Jun. 20, 2012,entitled “IMPROVED RESID HYDROTREATING CATALYST CONTAINING TITANIA”, allof which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to the catalytic hydrotreating of residuumfeed streams. In particular, the present invention relates to a methodfor the preparation of an improved catalyst carrier, an improvedhydrodesulfurization catalyst prepared using the carrier and a processfor hydrodesulfurizing a hydrocarbon feedstock while simultaneouslyreducing the microcarbon residue content of the treated feedstock usingthe aforementioned catalyst.

BACKGROUND OF THE INVENTION

Hydrocarbon feedstocks are typically combusted as a fuel. When thesehydrocarbon feedstocks contain sulfur, the combustion of the feedstocksproduces a pollutant of the atmosphere in the form of sulfur oxidegases. In the petroleum refining industry, it is often desirable toupgrade sulfur containing oil and fractions like heavy oils and residuumby hydrotreating to reduce the sulfur content of the fractions.

In the hydrotreating process, hydrocarbon feedstocks are contacted witha hydroconversion catalyst in the presence of hydrogen at elevatedpressure and temperature. Catalysts used in hydrotreating processesgenerally comprise catalytically active metals from Groups 6, 9 and 10of The Periodic Table and are typically supported on a support madepredominately of alumina. To achieve desulfurization, typical operatingconditions hydrotreating processes have included a reaction zonetemperature of 300° C. to 480° C. a pressure of 20 to 200 bar, ahydrogen feed rate of 90 to 2500 normal liters of hydrogen gas per liter(Nl/l) of oil feed, and a catalyst such as nickel or cobalt andmolybdenum or tungsten on a predominately alumina support.

In addition to upgrading the heavy oil or residuum stock to reducesulfur, it is highly desirable to upgrade the hydrocarbon feedstocks toprovide a low carbon residue.

Carbon residue is a measurement of the tendency of a hydrocarbon to formcoke. Expressed in weight percent, carbon residue may be measured asmicrocarbon residue (MCR). The MCR content in a hydrotreated residualfeedstock is an important parameter since the hydrotreated residueusually acts as feed to a coker or the fluid catalytic cracking (FCC)unit. Decreasing the MCR content in a hydrotreated residue decreases theamount of low value coke generated in the coker and increases the amountof gasoline generated in the FCC unit.

To this end, there remains a need to develop catalyst compositions whichprovide good hydrodesulfurization of heavy oil and residuum feedstockswhile simultaneously providing improved MCR conversion during ahydrotreating process.

SUMMARY OF THE INVENTION

The present invention is based on the finding that the use of aco-precipitated titania alumina support having a specified poredistribution unexpectedly provides an improved catalyst forhydrodesulfurization of hydrocarbon feedstocks, in particularly residuumfeedstocks, during a hydrotreating process as compared tohydrodesulfurization using catalysts prepared from an alumina supporthaving the same or substantially the same pore distribution.

Additionally, catalysts of the invention provide a reduced MCR contentin residue fractions. Hydrocarbon fractions obtained from ahydrotreating process using a catalyst in accordance with the inventionadvantageously exhibit a reduced MCR content as compared to the MCRcontent of the starting hydrocarbon feedstock. Further, hydrocarbonfractions obtained from a hydrotreating process using a catalyst inaccordance with the invention unexpectedly exhibit a reduced MCR contentwhen compared the MCR content obtained using a hydrodesulfurizationcatalyst having the same or substantially the same pore distribution andprepared from a support containing alumina alone.

In one aspect of the present invention, a catalyst support for preparingan improved hydrodesuflurization catalyst is provided. The catalystsupport comprises a co-precipitated titania alumina having 5 wt % orless titania, based on the total weight of the titania alumina, and hasa pore distribution such that at least 70 volume percent of its porevolume is in pores having a diameter between about 70 Å and about 130 Å,less than 5% of the pore volume is in pores having a diameter above 300Å, and less than 2% of the pore volume is in pores having a diameterabove 1000 Å.

In another aspect of the present invention, a process is provided forpreparing an improved hydrodesulfurization catalyst. The catalyst isprepared from a catalyst support material comprising a co-precipitatedtitania alumina having 5 wt % or less titania, based on the total weightof the titania alumina. Catalysts in accordance with the presentinvention are prepared by impregnating catalytically active Group 6, 9and 10 metals or precursor metal compounds, and optionally, phosphorouscompounds, on a support in accordance with the invention.

In another aspect of the present invention there are provided improvedhydrodesulfurization catalysts for reducing the content of sulfur in aresiduum hydrocarbon feed stock during a hydrotreating process.

In still another aspect of the present invention there are providedimproved hydrotreating catalysts which have the ability to reduce thecontent of sulfur in a residuum hydrocarbon feed stock during ahydrotreating process while simultaneously reducing the content ofmicrocarbon residue (MCR) in the hydrotreated hydrocarbon fraction.

The present invention also provides a method of making a co-precipitatedtitania alumina support having a distinctive pore size distribution.

In yet another aspect of the present invention improved hydrotreatingprocesses using supported catalyst compositions in accordance with thepresent invention are provided.

These and other aspects of the present invention are described infurther details below.

DETAILED DESCRIPTION OF THE INVENTION

The present invention generally provides catalyst compositions comprisedof catalytically active metals or precursor metal compounds of metals ofGroups 6, 9 and 10 of The Periodic Table, and optionally phosphorouscompounds, supported on a co-precipitated titania alumina support. Inone embodiment of the invention, the support material used to preparethe catalyst of the invention comprises titania alumina containing 5 wt% or less titania, based on the total weight of the titania aluminacomposition. In another embodiment of the invention, the supportmaterial comprises less than 5 wt % titania, based on the total weightof the titania alumina composition. In still another embodiment of theinvention the support material comprises from about 0.3 to about 4.5 wt% titania, based on the total weight of the titania alumina composition.

Titania alumina supports in accordance with the present inventiongenerally comprise at least 90 wt % of a co-precipitated titania aluminaas described herein. Preferably, the support material comprises at least95 wt %, most preferably, greater than 99 wt % of titania alumina, saidweight percent being based on the total weight percent of the support.The support material thus can “consist essentially of” theco-precipitated titania alumina as described herein. The phrase “consistessentially of” as used herein with regards to the composition of thesupport material is used herein to indicate that the support materialmay contain co-precipitated titania alumina and other components,provided that such other components do not materially affect orinfluence the catalytic properties of the final hydroconversion catalystcomposition.

Advantageously, titania alumina supports in accordance with the presentinvention possess specific properties of surface area, pore volume andpore volume distribution.

For purposes of the present invention, pore volume may be measured usingnitrogen porosimetry and mercury penetration porosimetry. Typically,pores having a diameter of 1000 Å or less are measured using nitrogenporosimetry while pores having a diameter of greater than 1000 Å aremeasured using mercury penetration porosimetry.

Pore volume as described herein is the volume of a liquid which isadsorbed into the pore structure of the sample at saturation vaporpressure, assuming that the adsorbed liquid has the same density as thebulk density of the liquid. The liquid used for nitrogen porosimetry isliquid nitrogen. The procedure for measuring pore volumes by nitrogenphysisorption is as disclosed and described in D. H. Everett and F. S.Stone, Proceedings of the Tenth Symposium of the Colstom ResearchSociety, Bristol, England: Academic Press, March 1958, pp. 109-110.

The mercury measurement of the pore volume and the pore sizedistribution of the alumina support material recited in the presentinvention may be obtained using any suitable mercury porosimeter capableof a pressure range of atmospheric pressure to about 4000 bar, with acontact angle, θ=140°, and a mercury surface tension of 0.49 N/m at roomtemperature.

Surface area as defined herein is determined by BET surface areaanalysis. The BET method of measuring surface area has been described indetail by Brunauer, Emmett and Teller in J. Am. Chem. Soc. 60 (1938)309-319, which is incorporated herein by reference.

The surface area of titania alumina supports of the invention rangesfrom about 180 m²/g to about 300 m²/g. In a preferred embodiment of theinvention, the surface area of the titania alumina supports ranges fromabout 220 m²/g to about 280 m²/g.

Titania alumina supports of the invention have a total pore volume inthe range from about 0.5 cc/g to about 1.1 cc/g. In a preferredembodiment of the invention, the total pore volume of the supportsranges from about 0.6 cc/g to about 0.8 cc/g.

Supports of the invention have a distinct pore volume distribution suchthat generally at least 70% of the total pore volume have pores in adiameter between about 70 Å to 130 Å, less than 5% of the total porevolume have pores in a diameter above 300 Å, as determined by nitrogenporosimetry, and less than 2% of the total pore volume having pores witha diameter above 1000 Å, as determined by mercury penetrationporosimetry.

In one embodiment of the invention, at least 79% of the total porevolume of the co-precipitated titania alumina support have pores in adiameter between about 70 Å to 130 Å.

In another embodiment of the invention, from about 0.4 to about 1.5% ofthe total pore volume of the co-precipitated titania alumina supporthave pores in a diameter above 1000 Å.

Titania alumina supports in accordance with the present invention areprepared by co-precipitating aqueous alumina sulfate and an amount oftitanyl sulfate sufficient to provide 5 wt % or less titania in aco-precipitated titania alumina powder. In accordance with thisembodiment, alumina sulfate and titanyl sulfate are mixed with anaqueous stream containing sodium aluminate and held at a pH of about 7.5to about 10.0 and a temperature of about 50° C. to about 80° C. toprecipitate a titania alumina powder. The precipitated powder isfiltered, washed with water and dried at a temperature ranging fromabout 150° C. to about 250° C. until a powder with a moisture content of20 wt % to 40 wt %, as analyzed by a moisture analyzer at 955° C., isachieved.

The dried titania alumina powder is thereafter treated with a peptizingagent to peptize the alumina powder. Suitable peptizing agents includebut are not limited to, strong monobasic acids (e.g. nitric acid,hydrochloric acid and the like); organic acids (e.g. formic acid, aceticacid, propionic acid and the like); and aqueous bases (e.g. ammoniumhydroxide and the like). The peptized alumina powder is then extrudedand dried at a temperature ranging from about 100° C. to about 150° C.for about 30 minutes to about 3 hours.

The dried extrudate is thereafter calcined at a temperature ranging fromabout 500° C. to 900° C. for about 1 hour to about 3 hour to obtain afinal support having the required pore structure. Preferably, the driedextrudate is calcined at a temperature ranging from about 650° C. toabout 870° C. for about 1 to about 2 hours to obtain the final support.

Extruded supports in accordance with the invention may have variousgeometric forms, such as cylinders, rings, and symmetric and/orasymmetric polylobes, for instance, tri- or quadrulobes. Nominal sizesof the extrudates may vary. The diameter usually ranges from about 1 mmto about 3 mm, and the length ranges from about 1 mm to about 30 mm. Inone embodiment of the invention, the diameter ranges from about 1.1 mmto about 1.2 mm and the length ranges from about 2 mm to about 6 mm. Aswill be understood by one skilled in the catalyst arts, catalystparticles produced from the supports will have a similar size and shapeas the support.

Catalysts in accordance with the invention are prepared by contactingthe titania alumina supports with an aqueous solution of at least onecatalytically active metal or precursor metal compound to uniformlydistribute the desired metal on the support. Preferably, the metalsand/or metal precursors are distributed uniformly throughout the poresof the support. In a preferred embodiment of the invention, thecatalysts are prepared by impregnation of the catalyst supports toincipient wetness with an aqueous solution of the desired catalyticallyactive metal or precursor compound.

Catalytically active metal and/or precursor metals compounds useful toprepare the catalyst composition of the invention, include, but are notlimited to metals or compounds of metals selected from the groupconsisting of Group 6 of The Periodic Table, Group 9 of The PeriodicTable, Group 10 of The Periodic Table and combinations thereof.Preferred Group 6 metals include, but are not limited to, molybdenum andtungsten. Preferred Groups 9 and 10 metals include, but are not limitedto, cobalt and nickel.

In a preferred embodiment of the invention the combinations of nickeland molybdenum catalytic agents are preferred. In a more preferredembodiment of the invention, the resulting catalyst comprises Moconcentrations in the range of about 5.0 to about 12.0 wt % and Niconcentrations in the range of about 1.0 to about 6.0 wt %, said wt %being based on the total weight of the catalyst composition.

Suitable precursor metal compounds of Groups 9 and 10 metals include,but are not limited to, metallic salts such as nitrates, acetates andthe like. Suitable precursor metal compounds of Group 6 metals include,but are not limited to, ammonium molybdate, molybdic acid, molybdenumtrioxide, and the like.

Catalytically active metals contemplated for use with the supports ofthe present invention are preferably used in the form of oxides and/orsulfides of the metals. Preferably, the catalytically active metals areused in the form of oxides.

Catalyst compositions of the invention may also comprise a phosphoruscomponent. In this case, the impregnating solution may also contain aphosphorus compound, e.g. phosphoric acid, phosphates, and the like, inaddition to the desired catalytically active metals or precursor metalcompounds. Concentrations in the range of up to about 3.5 wt % ofphosphorous, calculated as elemental phosphorous, based on the weight ofthe total catalyst composition, are suitable for use in the catalysts ofthe invention. In a preferred embodiment of the invention, phosphorousconcentrations in the range of about 0.3 to about 3.0 wt % ofphosphorous, calculated as elemental phosphorous, based on the weight ofthe total catalyst composition, are useful in the catalysts of theinvention.

Following treatment of the supports with aqueous solutions of thecatalytically active metal/s or precursor compound/s, the catalyst areoptionally dried at a temperature in the range of about 100° C. to about200° C. for about 30 minutes to about 2 hours. The dried catalyst isthereafter calcined at a temperature and for a time sufficient toconvert at least part, preferably all, of the metal components orprecursors to the oxide form. In one embodiment of the invention, thecatalyst is calcined at a temperature in the range of about 300° C. toabout 600° C. for about 30 minutes to about 3 hours. In a preferredembodiment of the invention, the catalyst is calcined at a temperatureranging from about 450° C. to about 550° C. for about 1 hour to about 2hours.

As will be clear to a person skilled in the art, there is a wide rangeof variations on the impregnating method used to support the catalyticactive metals on the catalyst supports. It is possible to apply aplurality of impregnating steps or the impregnating solutions maycontain one or more of the component or precursors to be deposited, or aportion thereof. Instead of impregnating techniques, dipping methods,spraying methods and the like can be used. In the case of multipleimpregnations, dipping, and the like, drying and/or calcining may becarried out as between steps.

Catalysts according to the invention exhibit an increased catalyticactivity and stability for hydrodesulfurization of residuum feedstockduring a hydrotreating process. The catalytic process of the presentinvention is basically directed to residuum feedstocks as opposed togas-oil feedstocks. Residua typically have greater than 10 ppm metals,whereas gas-oils nearly always have less than 10 ppm metals content.Thus, typical feedstocks useful in the present invention are “heavyoils” which include, but is not limited to, crude oil atmosphericdistillation column bottoms (reduced crude oil or atmospheric columnresiduum), or vacuum distillation column bottoms (vacuum residua). Themetals are believed to be present as organometallic compounds, possiblyin porphyrin or chelate-type structures, but the concentrations ofmetals referred to herein is calculated as parts per million pure metal.

Catalysts of the invention provide an increased micro carbon residue(MCR) conversion during a hydrotreating process underhydrodesulfurization conditions. Consequently, the hydrodesulfurizedhydrocarbon fraction obtained exhibits a reduced MCR content as comparedto the MCR content of the starting residuum feedstock. Further,hydrotreated hydrocarbon fractions obtained using the catalyst of theinvention unexpectedly exhibit a reduced MCR as compared to the MCRobtainable using hydrodesulfurization catalysts prepared from a supportcontaining alumina alone or alumina in combination with other refractoryinorganic materials such as silica and magnesia.

A hydrotreating process employing the catalyst compositions of thisinvention may be carried out under hydrodesulfurization processconditions in an apparatus whereby an intimate contact of the catalystcomposition with said residuum containing feedstock and a free hydrogencontaining gas is achieved, to produce a hydrocarbon-containing fractionhaving a reduced level of sulfur. In a preferred embodiment of theinvention, the hydrotreating process is carried out using a fixedcatalyst bed. The hydrotreating process can be carried out as a batchprocess or a continuous process using one or more fixed catalyst beds ora plurality of fixed bed reactors in parallel or in series.

Typical hydrodesulfurization process conditions useful in the inventioninclude, but are not limited to, temperatures between about 300° andabout 450° C., hydrogen pressures between about 120 and about 200 bar,H₂:oil (or residuum hydrocarbon feedstock) ratios between about 250 andabout 1400 Nl/l (normal liters of hydrogen gas per liter of oil feed),and space velocities (hr-¹) between about 0.2 and about 2.0. In oneembodiment of the invention, the operating conditions for a hydrocarbonfeedstock desulfurization process include a reaction zone temperature ofabout 371° C. to about 388° C., a hydrogen pressure of about 138 toabout 158 bar, and a hydrogen feed rate of about 880 to about 900 normalliters per liter of oil feed.

To further illustrate the present invention and the advantages thereof,the following specific examples are given. The examples are given asspecific illustrations of the claimed invention. It should beunderstood, however, that the invention is not intended to be limited tothe specific details set forth in the Examples.

All parts and percentages in the examples as well as the remainder ofthe specification that refers to solid compositions or concentrationsare by weight unless otherwise specified. However, all parts andpercentages in the examples as well as the remainder of thespecification referring to gas compositions are molar or by volumeunless otherwise specified.

Further, any range of numbers recited in the specification or claims,such as that representing a particular set of properties, units ofmeasure, conditions, physical states or percentages, is intended toliterally incorporate expressly herein by reference or otherwise, anynumber falling within such range, including any subset of numbers withinany range so recited. Unless otherwise specified or inconsistent withthe disclosure, all ranges recited herein include the endpoints,including those that recite a range “between” two values.

EXAMPLES Example 1

Aluminum sulfate solution, titanyl sulfate solution and water were mixedto form 50 gallons of solution containing 3.4% aluminum and 0.45%titanium. This aluminum and titanyl sulfate solution was added to astrike tank containing a heel of 165 gallons of water at 63° C.Simultaneously, an aqueous sodium aluminate solution containing 12%aluminum was added to the strike tank to maintain the slurry pH at 8.4.After all the aluminum and titanyl sulfate solution was added, thesodium aluminate solution flow continued to bring the pH of the slurryto 9.2.

The slurry was filtered to separate out the titania alumina mix, whichwas subsequently washed on the filter belt to remove residual sodium andsulfate. The resulting filter cake was then spray dried to obtain atitania alumina powder containing 3.5 g titania per 100 g of titaniaalumina.

Example 2

The titania alumina obtained in Example 1 (5000 g) was mixed with 52 gof concentrated nitric acid (70%) and 5107 g of water for 85 min into awet mix. This wet mix was then extruded using a four-inch extruder intoasymmetrical quadrilobe shaped extrudates (nominal diameter 0.05″). Theextrudates were dried overnight at 120° C. before being calcined at 650°C. for 1 hr in 8 liter per minute of air flow.

The calcined extrudates had the following properties: surface area 263m²/g; total pore volume 0.714 cc/g; the pore volume in pores having adiameter between 70 and 130 Å was 79% of total pore volume; the porevolume in pores having a diameter above 300 Å was 1.2% of total porevolume; and the pore volume in pores having a diameter above 1000 Å was0.52% of total pore volume. The calcined titania alumina supportcontained 3.5 wt % titania.

Example 3

A titania alumina catalyst support prepared as described in Example 2was impregnated with an aqueous metal solution containing 11.4% Mo, 3.1%Ni and 0.3% P. The aqueous solution was prepared using molybdenumtrioxide, nickel carbonate and phosphoric acid in water. The wetextrudates were transferred into muffle trays and covered withperforated aluminum foil. The muffle trays were placed in an oven at120° C. overnight.

The dried extrudates were then calcined at 538° C. for 30 min in 8 literper minute of air flow. The finished catalyst was designated Catalyst Aand contained 9.60% molybdenum, 2.52% nickel, 1.75% titanium, and 0.26%phosphorous. Properties of the catalyst were as described in Table 1below.

Example 4

A titania alumina catalyst support prepared as described in Example 2was impregnated with an aqueous metal solution containing 11.8% Mo, 3.2%Ni and 2.6% P. The solution was prepared from molybdenum trioxide,nickel carbonate and phosphoric acid. The wet extrudates weretransferred into muffle trays and covered with perforated aluminum foil.The muffle trays were placed in an oven at 120° C. overnight.

The dried extrudates were then calcined at 538° C. for 30 min in 8 literper minute of air flow. The finished catalyst was designated Catalyst Band contained 9.52% molybdenum, 2.49% nickel, 1.78% titanium, and 1.95%phosphorous. Properties of the catalyst were as described in Table 1below.

Example 5

A titania alumina powder was prepared as described in Example 1 with theexception that the strike tank contained a heel of 234 gallons of water.The final titania alumina powder contained 4.1 g titania per 100 g oftitania alumina. A titania alumina support was prepared as described inExample 2 except that 5000 g of the powder was mixed with 136 g ofconcentrated nitric acid and 5275 g of water for only 60 min beforeextrusion, drying and calcination.

The calcined extrudates had the following properties: surface area 267m²/g; total pore volume 0.674 cc/g; the pore volume in pores having adiameter between 70 and 130 Å was 71% of total pore volume; the porevolume in pores having a diameter above 300 Å was 1.78% of total porevolume; and the pore volume in pore having a diameter above 1000 Å was0.73% of total pore volume.

The titania alumina catalyst support was impregnated with an aqueousmetal solution containing 11.4% Mo, 3.1% Ni and 0.3% P and subsequentlycalcined at 510° C. for 1 h. The finished catalyst was designated asCatalyst C and contained 8.74% molybdenum, 2.20% nickel, 0.29%phosphorous and 1.99% titanium. Properties of the catalyst were asdescribed in Table 1 below.

TABLE 1 Properties of Support used in Catalysts Catalyst A Catalyst BCatalyst C Titania 3.5 3.5 4.1 Content, wt % PSD, vol % 70-130 Å 79% 79%71%   >300 Å 1.20 1.20 1.78 50-200 Å 93.0 93.0 89.7 >1,000 Å 0.52 0.520.73

Comparative Example 1

An alumina powder was precipitated as described in Example 1 except thatthe aluminum sulfate solution was mixed with only water and not titanylsulfate. The resulted alumina powder contained no detectable amount oftitania.

A portion of the alumina powder (5000 g) was mixed with 134 g ofconcentrated nitric acid and 4961 g of water for 60 min into a wet mix.The wet mix was then extruded using a four-inch extruder intoasymmetrical quadrilobe shaped extrudates (nominal diameter 0.05″). Theextrudates were dried overnight at 120° C. before being calcined at 650°C. for 1 hr in 8 liter per minute of air flow.

The calcined extrudates had the following properties: surface area 276m²/g; total pore volume 0.746 cc/g; the pore volume in pores having adiameter between 70 and 130 Å was 78% of total pore volume; the porevolume in pores having a diameter above 300 Å was 1.10% of total porevolume; and the pore volume in pores having a diameter above 1000 Å was0.96% of total pore volume. See Table 2 below.

The calcined extrudates were impregnated with an aqueous metal solutionprepared from molybdenum trioxide, nickel carbonate and phosphoric acidto obtain a finished catalyst designative Comparative Catalyst 1 whichcontained 8.49% molybdenum, 2.37% nickel, and 0.22% phosphorous with aless than detectable titanium content.

Comparative Example 2

750 g of a precipitated alumina powder prepared as described inComparative Example 1 above was mixed with 8.9 g of concentrated nitricacid, 51.3 g magnesium nitrate hexahydate and 630 g of water for 20 mininto a wet mix. The wet mix was then extruded using a two-inch extruderinto asymmetrical quadrilobe shaped extrudates (nominal diameter 0.05″).The extrudates were dried at 204° C. for two hours before being calcinedat 650° C. for 1 hr in 0.5 liter per minute of air flow to decomposemagnesium nitrate into magnesia.

The calcined extrudates had the following properties: surface area 284m²/g; total pore volume 0.82 cc/g; the pore volume in pores having adiameter between 70 and 130 Å was 71% of total pore volume; the porevolume in pores having a diameter above 300 Å was 3.17% of total porevolume; and the pore volume in pores having a diameter above 1000 Å was0.35% of total pore volume. The calcined extrudate contained 1.6 wt %magnesia.

The calcined extrudates were impregnated with an aqueous metal solutionprepared from molybdenum trioxide, nickel carbonate and phosphoric acidto obtain a finished catalyst designated Comparative Catalyst 2 whichcontained 8.96% molybdenum and 2.40% nickel, 0.83% P and 0.85%magnesium. Properties of the catalyst were as described in Table 2below.

Comparative Example 3

5000 g of a precipitated alumina powder prepared as described inComparative Example 1 above was mixed with 105 g of concentrated nitricacid, 114 g of fine titania particles, and 3835 g of water for 70 mininto a wet mix. The wet mix was extruded using a four-inch extruder intoasymmetrical quadrilobe shaped extrudates. The extrudates were driedovernight at 120° C. before being calcined at 650° C. for 1 hr in 8liter per minute of air flow. The calcined extrudates had the followingproperties: surface area 263 m²/g; total pore volume 0.720 cc/g; thepore volume in pores having a diameter between 70 and 130 Å was 79% oftotal pore volume; the pore volume in pores having a diameter above 300Å was 1.0% of total pore volume; and the pore volume in pores having adiameter above 1000 Å was 0.22% of total pore volume. The percentagepore volume in pores between 50 and 200 Å, and above 200 Å was 93.0, and1.85%, respectively. The calcined extrudates contained 3.5% titaniathrough comulling.

The calcined extrudates were impregnated and calcined at a temperatureof 350° C. to provide a finished catalyst. The catalyst was designatedas Comparative Catalyst 3 and contained 8.78% molybdenum and 2.46%nickel, 1.63% titanium and 0.22% phosphorous. Properties of the catalystwere as described in Table 2 below.

Comparative Example 4

Titania alumina powder (1521 g) precipitated as described in Example 1with the exception that the heel water in strike tank was at 57° C. andcontaining 3.6 g titania per 100 g of titania and alumina. The titaniaalumina powder was mixed with 15.2 g of concentrated nitric acid and1166 g of water for 5 min into a wet mix. This wet mix is then extrudedusing a four-inch extruder into asymmetrical quadrilobe shapedextrudates (nominal diameter 0.05″). The extrudates were dried overnightat 120° C. before being calcined at 704° C. for 1 hr. The calcinedextrudates had the following properties: surface area 280 m²/g; totalpore volume 0.963 cc/g; the pore volume in pores having a diameterbetween 70 and 130 Å was 62.7% of total pore volume; the pore volume inpores having a diameter above 300 Å was 16.1% of total pore volume; andthe pore volume in pores having a diameter above 1000 Å was 12.3% oftotal pore volume. The percentage pore volume in pores less than 50 Å,between 50 and 200 Å, and above 200 Å were 2.1%, 80.7%, and 17.2%,respectively.

An impregnation solution was prepared from 9.8 g of ammoniumheptamolybdate, 7.5 g of nickel nitrate hexahydrate, 18 g ofconcentrated ammonia solution (29%) and 10 mL water. 52 g of theimpregnation solution was sprayed onto the above base. The impregnatedbase was subsequently calcined at 510° C. for 1 hour to provide thefinished catalyst. The catalyst was designated as Comparative Catalyst 4and contained 9.04% molybdenum, 2.36% nickel, 1.88% titanium, with lessthan a detectable phosphorous content. Properties of the catalyst wereas described in Table 2 below.

TABLE 2 Properties of Support in Comparative Catalysts ComparativeComparative Comparative Comparative Catalyst 1 Catalyst 2 Catalyst 3Catalyst 4 Titania 0.00 0.00 3.5 3.6 Content, wt % PSD, vol % 70-130 Å78 71 79 62.7   >300 Å 1.10 3.17 1.00 16.1 50-200 Å 92.8 90.9 9380.7 >1,000 Å 0.96 0.22 0.22 12.3

Example 6

Catalysts of the invention were evaluated for hydrodesulfurization andMCR residue content. After being presulfided using dimethyl disulfide,Catalyst A, Catalyst B, Catalyst C and Comparative Catalyst 1, Catalyst2, Catalyst 3, and Catalyst 4 were contacted with Arabian Light residuumfeed, which feed had been passed through a standard commercialdemetallation catalyst in a continuous packed bed reactor. The overallLHSV and pressure used in processing the Arabian Light residuum throughthe catalyst system containing the demetallation catalyst and therespective demetallation catalyst was 0.35 h⁻¹ and 2167 psig. Thetemperature of the reactor containing the demetallation catalyst wasincreased from 365 to 377° C., the temperature of the reactor containingCatalysts A through C and Comparative Catalysts 1 through 4 wasincreased from 371 to 388° C. throughout the test. The properties of theArabian light residuum are shown in Table 3 below.

TABLE 3 Properties of feed used in Example 6 Micro Carbon Residue 9.87wt % API Gravity 5.7 Sulfur 0.29 wt % Hot Heptane Asphaltenes 0.94 wt %Nickel 0.9 ppm Vanadium 0.9 ppm 5 vol % TBP 15 F 95 vol % TBP 305 F

After the catalysts had been in service for 400 h and reached 388° C.,the results for sulfur and hydrotreated residue MCR content wererecorded in Table 4 below.

TABLE 4 MCR and Sulfur Level Results for Test Catalyst Samples ProductProduct CATALYST Mo % Ni % P % Ti % MCR % Sulfur % Catalyst A 9.60 2.520.26 1.75 3.27 0.22 Catalyst B 9.52 2.49 1.95 1.78 3.34 0.19 Catalyst C8.74 2.20 0.29 1.99 3.45 0.24 Comparative Catalyst 1 8.49 2.37 0.22 —3.69 0.26 Comparative Catalyst 2 8.96 2.40 0.83 — 3.71 0.28 ComparativeCatalyst 3 8.78 2.46 0.22 1.63 3.97 0.43 Comparative Catalyst 4 9.042.36 — 1.88 4.28 0.43

As shown in the Table 4 above, the residuum fraction processed usingCatalyst A contained 3.27% MCR and 0.22% sulfur, and the residuumfraction processed using Catalyst B contained 3.34% MCR and 0.19%sulfur. In comparison, the residuum fraction processed using ComparativeCatalyst 1 contained 3.69% MCR and 0.26% sulfur. This shows the benefitof incorporating titanium in the support via co precipitation.

The residuum fraction processed using Catalyst C contained 3.45% MCR and0.24% sulfur. This showed the effect of a decreased pore volumepercentage in the range of 70 to 130 Å for Catalyst C as compared toCatalyst A. The residuum fraction processed using Comparative Catalyst 2and Comparative Catalyst 3 contained 3.71% and 3.97% MCR and 0.28 and0.43% sulfur, respectively. The results obtained from these two examplesshowed that the catalyst prepared from a support containing magnesiumoxide or titania along with alumina made by co-mulling are lesseffective to reduce sulfur and MCR as compared to a catalyst preparedfrom the co-precipitated titania alumina support of the invention.

The residuum fraction processed using Comparative Catalyst 4 contained4.28% MCR and 0.43% sulfur, which shows that a catalyst prepared from asupport having a pore distribution outside of the pore distribution ofthe invention provides inferior MCR and sulfur reduction.

1-27. (canceled)
 28. A method for preparing a catalyst forhydrodesulfurization of residuum hydrocarbon feedstocks which methodcomprises: impregnating a porous extruded support comprising a titaniaalumina extrudate formed from a peptized co-precipitated titania aluminapowder having 5 wt % or less titania based on the total weight of thetitania alumina, said support having a total pore volume in the range offrom about 0.5 to about 1.0 cubic centimeters per gram, at least 70% ofthe total pore volume in pores having a diameter between about 70 Å andabout 130 Å, less than 5% of the total pore volume have pores in adiameter above 300 Å, as determined by nitrogen porosimetry, and lessthan 2% of the total pore volume in pores having a diameter above 1000Å, as determined by mercury penetration porosimetry with an aqueoussolution containing at least one catalytic agent or catalytic agentprecursor selected from the group consisting of a compound of Group 6metals of The Periodic Table, Group 9 metals of the Periodic Table,Group 10 metals of The Periodic Table, and combinations thereof, and aphosphorous compound in an amount which provides a phosphorousconcentration in the range of about 0.22 to about 3.0 wt % ofphosphorous, calculated as elemental phosphorous, based on the weight ofthe total catalyst composition, said compounds being thermallydecomposable to their corresponding metal oxides, and thereafter dryingand calcining the resulting impregnated support to provide a supportedcatalyst.
 29. A catalyst produced by the method according to claim 28.30. A catalyst suitable for use in hydrodesulfurization of residuumhydrocarbon feedstocks comprising: a) a support comprising aco-precipitated titania alumina having 5 wt % or less titania based onthe total weight of the titania alumina; and b) at least one catalyticagent comprising a metal selected from the group consisting of a Group 6metal of The Periodic Table, a Group 9 metal of The Periodic Table, aGroup 10 metal of The Periodic Table, phosphorous and combinationsthereof, and a phosphorous compound in an amount which provides aphosphorous concentration in the range of 0.22 to about 3.0 wt% ofphosphorous, calculated as elemental phosphorous, based on the weight ofthe total catalyst composition; wherein the support is characterized ashaving: (i) a total pore volume of from about 0.5 to about 1.0 cubiccentimeters per gram; (ii) at least 70% of the total pore volume inpores having a diameter between about 70 Å and about 130 Å; (iii) lessthan 5% of the total pore volume in pores having a diameter above 300 Å,as determined by nitrogen porosimetry; and (iv) less than 2% of thetotal pore volume in pores having a diameter above 1000 Å, as determinedby mercury penetration porosimetry.
 31. The catalyst of claim 30 whereinthe calcined support comprises at least 90 wt % of the co-precipitatedtitania alumina.
 32. The catalyst of claim 30 wherein the amount oftitania present in the co-precipitated titania alumina is an amount lessthan 5 wt %, based on the total weight of the titania alumina.
 33. Thecatalyst of claim 32 wherein the amount of titania present in theco-precipitated titania alumina is an amount from about 0.3 to about 4.5wt % titania, based on the total weight of the titania alumina.
 34. Thecatalyst of claim 30 wherein at least 79% of the total pore volume ofthe support is in pores having a diameter between about 70 Å and about130 Å; or (b) from about 0.40% to about 1.5% of the total pore volume isin pores having a diameter above 1000 Å; or both (a) and (b).
 35. Thecatalyst of claim 30 wherein said at least one catalystic agentcomprises a metal selected from the group consisting of cobalt, nickel,molybdenum, and combinations thereof.
 36. The catalyst of claim 30wherein the phosphorous concentration is in the range of 0.22 to 1.95 wt% of phosphorous, calculated as elemental phosphorous, based on theweight of total catalyst composition.
 37. The catalyst of claim 30wherein the phosphorous concentration is in the range of about 0.26 to1.95 wt % of phosphorous, calculated as elemental phosphorous, based onthe weight of the total catalyst composition.
 38. A process forhydrotreating sulfur containing residuum hydrocarbon feedstocks, whichprocess comprises contacting said residuum feedstocks with a catalyst ofclaim 30 under hydrodesulfurization process conditions and producing ahydrotreated residuum hydrocarbon fraction having a reduced sulfurcontent compared to the residuum hydrocarbon feedstock.
 39. The processof claim 38 wherein the residuum hydrocarbon feedstock is contacted withthe catalyst at a reaction temperature from about 300° C. to about 450°C., a hydrogen pressure of about 120 bar to about 200 bar, a H₂:oilratio ranging from about 250 Nl/l to about 1400 Nl/l, and a spacevelocity from about 0.2 hr⁻¹ to about 2.0 hr⁻¹.